#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>

// MD5算法实现（不依赖OpenSSL）
typedef struct {
    uint32_t state[4];
    uint32_t count[2];
    unsigned char buffer[64];
} MD5_CTX;

#define F(x, y, z) (((x) & (y)) | ((~x) & (z)))
#define G(x, y, z) (((x) & (z)) | ((y) & (~z)))
#define H(x, y, z) ((x) ^ (y) ^ (z))
#define I(x, y, z) ((y) ^ ((x) | (~z)))

#define ROTATE_LEFT(x, n) (((x) << (n)) | ((x) >> (32-(n))))

#define FF(a, b, c, d, x, s, ac) { \
    (a) += F ((b), (c), (d)) + (x) + (uint32_t)(ac); \
    (a) = ROTATE_LEFT ((a), (s)); \
    (a) += (b); \
}

#define GG(a, b, c, d, x, s, ac) { \
    (a) += G ((b), (c), (d)) + (x) + (uint32_t)(ac); \
    (a) = ROTATE_LEFT ((a), (s)); \
    (a) += (b); \
}

#define HH(a, b, c, d, x, s, ac) { \
    (a) += H ((b), (c), (d)) + (x) + (uint32_t)(ac); \
    (a) = ROTATE_LEFT ((a), (s)); \
    (a) += (b); \
}

#define II(a, b, c, d, x, s, ac) { \
    (a) += I ((b), (c), (d)) + (x) + (uint32_t)(ac); \
    (a) = ROTATE_LEFT ((a), (s)); \
    (a) += (b); \
}

static void MD5Transform(uint32_t state[4], const unsigned char block[64]);
static void Encode(unsigned char *output, uint32_t *src, unsigned int len);
static void Decode(uint32_t *output, const unsigned char *src, unsigned int len);
static void MD5_memcpy(unsigned char *output, const unsigned char *src, unsigned int len);
static void MD5_memset(unsigned char *output, int value, unsigned int len);

// MD5初始化
void MD5Init(MD5_CTX *context) {
    context->count[0] = context->count[1] = 0;
    context->state[0] = 0x67452301;
    context->state[1] = 0xEFCDAB89;
    context->state[2] = 0x98BADCFE;
    context->state[3] = 0x10325476;
}

// MD5更新
void MD5Update(MD5_CTX *context, const unsigned char *src, unsigned int srcLen) {
    unsigned int i, index, partLen;

    // 计算已有字节数
    index = (unsigned int)((context->count[0] >> 3) & 0x3F);

    // 更新比特数
    if ((context->count[0] += ((uint32_t)srcLen << 3)) < ((uint32_t)srcLen << 3))
        context->count[1]++;
    context->count[1] += ((uint32_t)srcLen >> 29);

    partLen = 64 - index;

    // 填充缓冲区
    if (srcLen >= partLen) {
        MD5_memcpy(&context->buffer[index], src, partLen);
        MD5Transform(context->state, context->buffer);

        for (i = partLen; i + 63 < srcLen; i += 64)
            MD5Transform(context->state, &src[i]);

        index = 0;
    } else {
        i = 0;
    }

    // 保存剩余数据
    MD5_memcpy(&context->buffer[index], &src[i], srcLen - i);
}

// MD5最终处理
void MD5Final(unsigned char digest[16], MD5_CTX *context) {
    unsigned char bits[8];
    unsigned int index, padLen;

    // 保存比特数
    Encode(bits, context->count, 8);

    // 计算填充长度
    index = (unsigned int)((context->count[0] >> 3) & 0x3F);
    padLen = (index < 56) ? (56 - index) : (120 - index);

    // 添加填充
    MD5Update(context, (unsigned char *)"\200", 1);
    while (padLen-- > 1)
        MD5Update(context, (unsigned char *)"\0", 1);

    // 添加比特数
    MD5Update(context, bits, 8);

    // 保存结果
    Encode(digest, context->state, 16);

    // 清理敏感信息
    MD5_memset((unsigned char *)context, 0, sizeof(*context));
}

// MD5转换函数
static void MD5Transform(uint32_t state[4], const unsigned char block[64]) {
    uint32_t a = state[0], b = state[1], c = state[2], d = state[3], x[16];

    Decode(x, block, 64);

    // 第一轮
    FF(a, b, c, d, x[ 0],  7, 0xd76aa478);
    FF(d, a, b, c, x[ 1], 12, 0xe8c7b756);
    FF(c, d, a, b, x[ 2], 17, 0x242070db);
    FF(b, c, d, a, x[ 3], 22, 0xc1bdceee);
    FF(a, b, c, d, x[ 4],  7, 0xf57c0faf);
    FF(d, a, b, c, x[ 5], 12, 0x4787c62a);
    FF(c, d, a, b, x[ 6], 17, 0xa8304613);
    FF(b, c, d, a, x[ 7], 22, 0xfd469501);
    FF(a, b, c, d, x[ 8],  7, 0x698098d8);
    FF(d, a, b, c, x[ 9], 12, 0x8b44f7af);
    FF(c, d, a, b, x[10], 17, 0xffff5bb1);
    FF(b, c, d, a, x[11], 22, 0x895cd7be);
    FF(a, b, c, d, x[12],  7, 0x6b901122);
    FF(d, a, b, c, x[13], 12, 0xfd987193);
    FF(c, d, a, b, x[14], 17, 0xa679438e);
    FF(b, c, d, a, x[15], 22, 0x49b40821);

    // 第二轮
    GG(a, b, c, d, x[ 1],  5, 0xf61e2562);
    GG(d, a, b, c, x[ 6],  9, 0xc040b340);
    GG(c, d, a, b, x[11], 14, 0x265e5a51);
    GG(b, c, d, a, x[ 0], 20, 0xe9b6c7aa);
    GG(a, b, c, d, x[ 5],  5, 0xd62f105d);
    GG(d, a, b, c, x[10],  9, 0x02441453);
    GG(c, d, a, b, x[15], 14, 0xd8a1e681);
    GG(b, c, d, a, x[ 4], 20, 0xe7d3fbc8);
    GG(a, b, c, d, x[ 9],  5, 0x21e1cde6);
    GG(d, a, b, c, x[14],  9, 0xc33707d6);
    GG(c, d, a, b, x[ 3], 14, 0xf4d50d87);
    GG(b, c, d, a, x[ 8], 20, 0x455a14ed);
    GG(a, b, c, d, x[13],  5, 0xa9e3e905);
    GG(d, a, b, c, x[ 2],  9, 0xfcefa3f8);
    GG(c, d, a, b, x[ 7], 14, 0x676f02d9);
    GG(b, c, d, a, x[12], 20, 0x8d2a4c8a);

    // 第三轮
    HH(a, b, c, d, x[ 5],  4, 0xfffa3942);
    HH(d, a, b, c, x[ 8], 11, 0x8771f681);
    HH(c, d, a, b, x[11], 16, 0x6d9d6122);
    HH(b, c, d, a, x[14], 23, 0xfde5380c);
    HH(a, b, c, d, x[ 1],  4, 0xa4beea44);
    HH(d, a, b, c, x[ 4], 11, 0x4bdecfa9);
    HH(c, d, a, b, x[ 7], 16, 0xf6bb4b60);
    HH(b, c, d, a, x[10], 23, 0xbebfbc70);
    HH(a, b, c, d, x[13],  4, 0x289b7ec6);
    HH(d, a, b, c, x[ 0], 11, 0xeaa127fa);
    HH(c, d, a, b, x[ 3], 16, 0xd4ef3085);
    HH(b, c, d, a, x[ 6], 23, 0x04881d05);
    HH(a, b, c, d, x[ 9],  4, 0xd9d4d039);
    HH(d, a, b, c, x[12], 11, 0xe6db99e5);
    HH(c, d, a, b, x[15], 16, 0x1fa27cf8);
    HH(b, c, d, a, x[ 2], 23, 0xc4ac5665);

    // 第四轮
    II(a, b, c, d, x[ 0],  6, 0xf4292244);
    II(d, a, b, c, x[ 7], 10, 0x432aff97);
    II(c, d, a, b, x[14], 15, 0xab9423a7);
    II(b, c, d, a, x[ 5], 21, 0xfc93a039);
    II(a, b, c, d, x[12],  6, 0x655b59c3);
    II(d, a, b, c, x[ 3], 10, 0x8f0ccc92);
    II(c, d, a, b, x[10], 15, 0xffeff47d);
    II(b, c, d, a, x[ 1], 21, 0x85845dd1);
    II(a, b, c, d, x[ 8],  6, 0x6fa87e4f);
    II(d, a, b, c, x[15], 10, 0xfe2ce6e0);
    II(c, d, a, b, x[ 6], 15, 0xa3014314);
    II(b, c, d, a, x[13], 21, 0x4e0811a1);
    II(a, b, c, d, x[ 4],  6, 0xf7537e82);
    II(d, a, b, c, x[11], 10, 0xbd3af235);
    II(c, d, a, b, x[ 2], 15, 0x2ad7d2bb);
    II(b, c, d, a, x[ 9], 21, 0xeb86d391);

    state[0] += a;
    state[1] += b;
    state[2] += c;
    state[3] += d;

    // 清理敏感信息
    MD5_memset((unsigned char *)x, 0, sizeof(x));
}

// 编码函数
static void Encode(unsigned char *output, uint32_t *src, unsigned int len) {
    unsigned int i, j;

    for (i = 0, j = 0; j < len; i++, j += 4) {
        output[j] = (unsigned char)(src[i] & 0xff);
        output[j+1] = (unsigned char)((src[i] >> 8) & 0xff);
        output[j+2] = (unsigned char)((src[i] >> 16) & 0xff);
        output[j+3] = (unsigned char)((src[i] >> 24) & 0xff);
    }
}

// 解码函数
static void Decode(uint32_t *output, const unsigned char *src, unsigned int len) {
    unsigned int i, j;

    for (i = 0, j = 0; j < len; i++, j += 4)
        output[i] = ((uint32_t)src[j]) | (((uint32_t)src[j+1]) << 8) |
                    (((uint32_t)src[j+2]) << 16) | (((uint32_t)src[j+3]) << 24);
}

// 内存操作函数
static void MD5_memcpy(unsigned char *output, const unsigned char *src, unsigned int len) {
    unsigned int i;

    for (i = 0; i < len; i++)
        output[i] = src[i];
}

static void MD5_memset(unsigned char *output, int value, unsigned int len) {
    unsigned int i;

    for (i = 0; i < len; i++)
        ((char *)output)[i] = (char)value;
}

// 将MD5哈希值转换为32位字符串（大小写可选）
void MD5To32String(unsigned char digest[16], char *output, int uppercase) {
    const char *hex_chars = uppercase ? "0123456789ABCDEF" : "0123456789abcdef";
    for (int i = 0; i < 16; i++) {
        output[i*2] = hex_chars[(digest[i] >> 4) & 0xF];
        output[i*2+1] = hex_chars[digest[i] & 0xF];
    }
    output[32] = '\0';
}

// 将MD5哈希值转换为16位字符串（大小写可选）
void MD5To16String(unsigned char digest[16], char *output, int uppercase) {
    const char *hex_chars = uppercase ? "0123456789ABCDEF" : "0123456789abcdef";
    // 取中间16个字符（第9到24个字符）
    for (int i = 4; i < 12; i++) {
        output[(i-4)*2] = hex_chars[(digest[i] >> 4) & 0xF];
        output[(i-4)*2+1] = hex_chars[digest[i] & 0xF];
    }
    output[16] = '\0';
}

// int main(int argc, char *argv[]) {
//     if (argc < 2) {
//         printf("用法: %s <字符串> [选项]\n", argv[0]);
//         printf("选项:\n");
//         printf("  -32u: 32位大写MD5\n");
//         printf("  -32l: 32位小写MD5 (默认)\n");
//         printf("  -16u: 16位大写MD5\n");
//         printf("  -16l: 16位小写MD5\n");
//         return 1;
//     }

//     const char *src = argv[1];
//     int option = 0; // 0: 32位小写(默认), 1: 32位大写, 2: 16位小写, 3: 16位大写

//     // 检查选项参数
//     if (argc > 2) {
//         if (strcmp(argv[2], "-32u") == 0) {
//             option = 1;
//         } else if (strcmp(argv[2], "-16l") == 0) {
//             option = 2;
//         } else if (strcmp(argv[2], "-16u") == 0) {
//             option = 3;
//         } else if (strcmp(argv[2], "-32l") != 0) {
//             printf("未知选项: %s\n", argv[2]);
//             return 1;
//         }
//     }

//     MD5_CTX context;
//     unsigned char digest[16];
//     char output[33]; // 32个字符 + 终止符

//     // 计算MD5
//     MD5Init(&context);
//     MD5Update(&context, (unsigned char *)src, strlen(src));
//     MD5Final(digest, &context);

//     // 根据选项生成相应格式的MD5字符串
//     switch (option) {
//         case 0: // 32位小写
//             MD5To32String(digest, output, 0);
//             break;
//         case 1: // 32位大写
//             MD5To32String(digest, output, 1);
//             break;
//         case 2: // 16位小写
//             MD5To16String(digest, output, 0);
//             break;
//         case 3: // 16位大写
//             MD5To16String(digest, output, 1);
//             break;
//     }

//     printf("原始字符串: %s\n", src);
//     printf("MD5 %s: %s\n", 
//            option == 0 ? "32位小写" : 
//            option == 1 ? "32位大写" : 
//            option == 2 ? "16位小写" : "16位大写", 
//            output);

//     return 0;
// }  

void md5_encode(const char *src, char * dest, int option)
{
    MD5_CTX context;
    unsigned char digest[16];
    char output[33]; // 32个字符 + 终止符

    // 计算MD5
    MD5Init(&context);
    MD5Update(&context, (unsigned char *)src, strlen(src));
    MD5Final(digest, &context);

    // 根据选项生成相应格式的MD5字符串
    switch (option) {
        case 0: // 32位小写
            MD5To32String(digest, output, 0);
            break;
        case 1: // 32位大写
            MD5To32String(digest, output, 1);
            break;
        case 2: // 16位小写
            MD5To16String(digest, output, 0);
            break;
        case 3: // 16位大写
            MD5To16String(digest, output, 1);
            break;
    }

    sprintf(dest,"%s", output);

}

// int main()
// {
//     char str[1024] = "hello";
//     char str1[33] = {0};
//     md5_encode(str, str1, 0);
//     printf("%s\n",str1);

//     return 0;
// }